Electrolytic recording



Jan. 18, 1949.

H. G. GREIG ELECTROLYTIC RECORDING Filed Oct. 14, L944 INVEN TOR. fmpam6; 6/954;

ATTORNEY Patented Jan. 18, 1949 ELECTROLYTIC RECORDING Harold G. Greig,Princeton, N. J., assignor to Radio Corporation of America, acorporation of Delaware Application October 14, 1944, Serial No. 558,717

12 Claims.

The present invention relates to the electrolytic production of azo dyesin the form of images on a traveling web or band and particularly to theproduction of such dyestuff images in facsimile recording whileemploying as a component for the production of the dyestufi images, astabilized diazo amino compound.

It has been proposed in the past to produce images or records on areceiver by means of an electromagnetically controlled printer barspecifically in connection with facsimile recording. By the termfacsimile recording as used herein is meant not only the reproduction onthe receiver of'a pie-existing subject but also the reception ofsubject-matter in the process of creation or formation. This method hasbeen found to give satisfactory records. However, the method is notentirely free from objection, particularly from the standpoint of thespeed at which the records are made and the wear on the printer bar.

In an effort to improve upon this method, experimentation was conductedwith recording involving the utilization of an electrolytic currentdesigned to produce on the receiver, azo dyestufi images or records.Three methods were devised for the purpose of effecting this result, onecomprising the electrolytic diazotization of a primary aromatic amineand an electrolytic coupling of the so-formed diazonium compound with acoupling component, another comprising the electrolytic coupling of apreformed diazonium salt with a coupling compound, and the thirdcomprising the electrolytic oxidation of an oxidizable dye. These threemethods, as compared to the electromagnetically controlled printer barmethod have the advantages of speed and avoidance of wear. on therecording parts of the mechanism. Of these three methods, the first wasfound to be the most efficacious. The second method, involving theelectrolytic coupling of a diazonium salt, has the disadvantage that thediazonium salt is light-sensitive and hence of little stability. Thethird method, involving electrolytic oxidation, employs compounds whichare oxidizable by the oxygen in the air. The receiver impregnated withthese compounds is therefore not storage stable. .Furthermo're, sincethe compounds are oxidizable in the air, the records obtained do nothave background permanence due to air oxidavtion of the compounds on thereceiver at the good records, the records do not represent the optimumin these two important aspects: (1) :shade and depth of color of theimages and (2) background permanence,

The azo dyeswhich give the best records are dark blue, green and blackdyes. While there are many components employed in the manufacture of azodyestuffs which yield yellow, orange and red dyes, there are not so manycomponents which give dyes simulating a black shade. The monoazo dyeswhich possess such shades are metal complexes of the dyestufi, usuallywith a metal such as chromium. The other dyes having such shade aretrisazo dyes. The difficulties of introducing a metal into a preformeddye serving as an image record with the production of a modified record,are self-evident. Attempts to produce satisfactory records in this waymet with little or no success.

It is of course possible to produce a record of a trisazo dye bystarting with a receiver which is dyed with a monoazo dye and byeffecting the formation of the 'trisazo dye under the printer bar. This,however, means that the receiver is originall dyed, making it difficultand complex to handle the receiver prior to its use.

There are certain primary amines which upon diazotization and couplingyield deep blue dyes. Primary amines of this character are benzidine,dianisidine and the like. These compounds, however, are insoluble inwater and hence cannot be used in the electrolytic diazotization andcoupling method.

It has been found thatwith the electrolytic diazotization and couplingmethod, the impermanence of the background is attributable to threepossible factors. The first of these involves the spontaneous formationof the dyestuff of which the record is composed. The coloring producedin this way, however, is dischargeable by alkaline sodium hydrosuifitesolution. Another possibility involves oxidation of the coupler. Thecolor thus produced also appears to be dischargeable. The third factorinvolves oxidation and polymerization and the color produced in this Wayis not dischargeable.

It has been found that coloring produced by the last of these methods isenhanced by primary aromatic amino groups, particularly when these arepresent in the coupling component. Attempts to modify these groups Or tomodif the structure of the various couplers used in the electrolyticdiazotization and coupling method so as to avoid this latter type ofcoloration have given some improvement but have not completelyalleviated the condition.

It has now been discovered that the disadvantages inherent in theutilization of the electrolytic diazotization and coupling method can benicely avoided by producing the image records by reacting undcr theinfluence of an electrolytic current, a coupling compound with adiazonium compound stabilized by means of an organic amine. Thesecompounds are known in the dyestufi art as diazoamino compounds. Suchcomof an electrolytic current, a diazoamino com pound and a couplingcompound.

It is a further object of this invention to produce color images byreacting under the influence of an electrolytic current a diazoamin'ocompoundand a coupling compound.

It is a further object of thisinvention to electrolytically produce azodyestufi records which are of a dark shade simulating black and whichhave improved background stability.

It is a further object of thisz invention to pro duce dyestuffl image.records by' submitting to electrolysis a. diazoamino compound and acoupling': compound while insuring regeneration of thevdiazoniumcompound forcoupling withth'e.

coupling compound;

Itiisla'nfurther objectofthiszinvention to producedyestufiszimagerrecords whileutilizing as one i of? the components:water-insoluble: primary aromatic'uamines;

It is; a further: object of. this: invention 7 to" stasbilize thecoupling compound used inxtherformation: of azo dyestuffr images. byvelectrolysis;

It is a further object of this invention to deepen the shadesofelectrolyticallyproduced dyestufi imagerecordsbyincreasingtheconcentration of the dyestuffs: insaid images;

Other and further" objects: willbecome apparent as :the descriptionproceeds.

It has beenrpointed out that' the diazoamino compounds. with 4 whichthe; present invention is concernedhave been utilized in theadyestufi;art. These diazoamino compoundsrare obtained by reacting inian' alkalinesolution a.- diazonium compound with an organic amine. which doescnot.eas-

ily, couple to form an azotdye. The'product which. isthus obtained: is:capable. of regenerating the diazom'um compound upon treatment with. hotsteam;.acid vapors; strong-acids and'the like. If this;regenerationzberaefie'cted in the: presenceof a coupling compound,coupling,v ensues: with: the formation of a dyestufi image.

lnitherdyestuff art; these. compoundssare used in one of. two methods;In the first method; fabricsandthe likearei uniformly dyed by; imepregnating, the fabric: with: the: stabilized diae zonium compound and;regenerating: the;diazoni;- um compound .inthe presence ofra.couplingcomepound; The second method involves printing a design-,ona.fabric with a paste containing," the diazoamino compound and .acoupling. compound and regenerating: the diazonium compound by anaiterdevelopment procedure. It will become apparent-fromv whatv willbesubsequently stated; that the presentmethod. in its. contemplation ofthe use of the diazoamino compounds isvclearly distinguished from theutilization of such diazo+ aminocompounds 'in the dyestufi art.

,The diazoamino compounds may beformulistically represented as follows:

wherein A isan arylradical, and X is a radical of an organic amine, theamino nitrogen atom of which is linked totheazo group; When thesecompounds are treated with-steam, an acid or the hot vapors' of an acid,the'compounds are split along the dotted line-indicated in the for mula.The diazonium compound whicli has thus Til been sprung is now capable ofreacting with a coupling compound of the type usual in the formation" ofazoidye's to give a dyestuff;

The diazoamino compounds falling within the above general classificationand which have been found suitable for use in my process may be morespecifically classified under the following formulae:

, R1 A'[N=NN/ Ra In these formulae',,R1- andRlarehydrogen; an aliphatic,araliphatic; cy'c'loaliphaticoraromati'c radical, R2 an'd'Rl are'an'aliphatic; aralipliatic; cycloaliphatic oraromatic." radical, A and: A"are.

' aromatic radicals, Z"represents theatoms' neces sary to complete: a"nitrogenous heterocyclic" ring system; and :ris l'or 25 Suitablealiphatic radicals as represented by; R1,.R2, R3. and R4 are alkyl.radicals, such? as ethyl, methyLpropyLbutyl, isopropyll isobutyl, amylj,octyl andthe like; hydi'oxyalkyl radicals such as: ethanol; propano-l,butanol, hexanohand the. like, carboxyalkyl radicals; such as carboxyethyl; carboxy methyl, carboxy propyl, carboxy, butyl and the" like,sulfo alkyl radicals; such as sulfo' methyl, .sulfo ethyl; sulfo propyl,.sulfo: butyl and" the like; Suitable? araliphatic values? forRi; R2, RiandRii are benyl and the like; The cycle? aliphatic radicals may becyclopentyl; cyifloliexyl',- hydroxycyclohexyl, sulfo'cyclo'liexyl;carb'oxycy, c'lohexyl and the like: The" aromatic" radicalscontemplatedby' Bi and R2" may' be mon'osulfo benzoic acid,"disulfobenzoic acid and the like;

The aromatic radicals represented by A and A" are members'ofthe-benzene, naphthalene; an thracene; diph'enyl; and" diphenyl" ether:series; The and rings of these radicals may contain substituents such asalkyl, such as ethyl} methyl, propyl and the' lilde; alkoxy, such as-m'ethoxy, ethoxy and the like, halogen, such as chlorine and bromine,nitro; amino; ac-ylamino; sucli as acetylamino, benzoylamin'o;naphthoylami'n'o; and the like, carboxy-a-ndsulfonic-acidfigroupss carbamyl such as benzene carb'amyl; 8 hyd'r'oxy-3-6' disulfo naphthalenecarbamylland tlie likee may be a pyridine, such as amino-alpha-carboxypyridine, amino-pyridine sulfonic acid, aminopyridine, dicarboxypyridine, and the like, pyrroles, such as alpha-carboxy pyrrolidine,alphai-alpha- -carboxy pyrrolidine, pyrrolidine alpha sulfonic acid andthe like, piperidines such as piperidine, beta-carboxy piperidine,alpha-carboxy piperidine, piperidine-gamma-sulfomc acid, morpholine,carbazole, tetrahydraquinoline, tetrahydracarbazole, hexahydrocarbazoleand the like. Many of these compounds and their methods of preparationare known in the dyestufi art, as may be seen from a reference to U. S.P. 1,882,- 556; 1,882,561; 2,005,347; 2,051,148; 2,078,387 and2,099,091.

Specific primary aromatic amines which after diazotization may beconverted to diazoamino compounds by treatment with an organic amine,and specific organic amines suitable for such conversion are listedbelow:

AMINES TO BE DIAZOTIZED Benzidine Dianisidine Naphthionic acid Alphanaphthylamine-4.8-disulfonic acid Alpha naphthylamine--sulfonic acidBeta naphthylamine-5-sulfonic acid 1-amino-naphthalene-3.6-disulfonicacid Anthranilic acid Benzidine-3.3-disulfonic acid4-diethanolamine4-amino azo benzene l-amino diphenylene oxide l-aminodiphenylene sulfide 1-amino-2-meth0xy-5-chloro benzene 1-aminoanthracene 4-amino diphenyl 6-amino-3-benzoylamino-1.4-diethoxy benzenetolidine and the like.

STABILIZING AMINES Ethanolamine Diethanolamine SarcosineDiisopropanolamine Morpholine Cyclohexylamine 2-5-dihydroxydicyclohexylamine -3'- carboxylic acid p-hydroxy cyclohexenyl glycineMethyl glucamine Alpha-carboxy pyrrolidine Alpha-1-a1pha-2-dicarboxypyrrolidine Carboxy-piperidine Loiponic acid Beta-carboxy-piperidineTetrahydroquinoline Piperidine Carbazole Diglycolamino acidBenzyl-xylamine 4-sulfo-2-amino benzoic acid Dibenzylamine-disulfonicacid Taurine Cyclohexylamino-acetic acid 2-methylamino-4-sulfo benzoicacid Methyl mannamine Dimethylamine Diethylamine 'Dibutylamine Examplesof stable diazoami'no compounds i1'- lustrative of those which I haveemployed in carrying out the invention are the following:

1 mol of diazotized 4'-diethanolamino-4-aminoazobenzene 1 mol ofdiethanolamine 1 mol of tetrazotized dianisidine 2 moles ofdiethanolamine 1 mol of tetrazotized benzidine-3.3-disulfonic acid 2moles of diethanolamine 1 mol of tetrazotized benzidine 2 moles ofdiethanolamine 1 mol of diazotized naphthionic acid 1 mol ofdiethanolamine 1 mol of diazotized naphthionic acid 2 moles ofdiethanolamine 1 mol of diazotized naphthionic acid 1 mol of diisopropanolamine 1 mol of diazotized naphthionic acid 1 mol ofmonoethanolamine 1 mol of diazotized naphthionic acid 1 mol ofmorpholine 1 mol of diazotized alpha naphthylamine-4.8- disulfonic acid1 mol of diethanolamine 1 mol of diazotized alpha naphthylamine-4.8-disulfonic acid 2 moles of diethanolamine 1 mol of diazotized alphanaphthylamine-5- sulfonic acid 1 mol of diethanolamine 1 mol ofdiazotized beta naphthylamine-B-sulionic acid 1 mol of diethanolamine 1mol of diazotized naphthy1amine-3.6-disulfonic acid 1 mol ofdiethanolamine 1 mol of diazotized anthranilic acid 1 mol ofdiethanolamine 1 mol of tetrazotized dianisidine 2 mols of sarcosine 1mol of diazotized naphthionic acid 1 mol of cyclohexylamine 1 mol ofdiazotized naphthionic acid 1 molof 2.5-dihydroxy dicyclohexylamine -3'-carboxylic acid 1 mol of diazotized naphthionic acid 1 mol of p-hydroxycyclohexenyl glycine 1 mol of diazotized naphthionic acid 1 mol ofdibutylamine 1 mol of diazotized naphthionic acid 1 mol ofdi-Z-ethylhexylamine 1 mol of diazotized naphthionic acid 1 mol of4-sulfo-2-amino benzoic acid 1 mol of tetrazotized dianisidine 2 mols of4-sulfo-2-amino benzoic acid 1 mol of diazotized naphthionic acid 1 molof alpha-hydroxy pyrrolidine 1 mol of diazotized naphthionic acid 1 molof gamma-hydroxy piperidine 1 mol of diazotized naphthionic acid 1 molof carbazole-Z-sulfonic acid 1 mol of diazotized naphthionic acid 1 molof alpha carboxy pyrrolidine 1 mol of diazotized naphthionic acid 2 molsof morpholine The diazoamino compounds are employed with any of thecouplers usual in the manufacture of azo dyestuffs. A list of couplerswhich ma be employed are, for instance, disclosed in Solomon U. S. P.2,306,471. It is to be borne in mind,

however, that certain couplers give better results than others, and thisis particularly true with regard to chromotropic acid. Other couplers bywhich very satisfactory records can be obtained are:

p-Sulfo-phenyl methyl pyrazolone H acid Phenyl I acid Chloro H acid1-naphthol-4.8-disulfonic acid Acetyl H acid Naphthol AS "Beta naphtholNaphthol RF Ethylated beta naphthol A mixture of chromotropic acid anddiacetoacetyl ethlyene diamine.

Of these various couplers, chromotropic acid. has been found to giverecords which excel from the standpoint of darkness of shade andbackground permanence and the chromotr'opic acid is therefore preferred.

It has been previously stated that the diazoamino compounds are preparedaccording'to the prior art by diazotizin-g a primary aromatic amine andreacting therewith in an alkaline solution, an organic amine that doesnot easily couple to form azo dyes. It has been found that the relativeproportions of the amine acting as a stabilizer to the diazoniumcompound is of marked significance In any case, it is necessary to usean excess of the stabilizing amine over the quantity theoreticallyrequired to produce stabilized diazonium compounds. If the diazo'aminocompound is insoluble, there should be used in itspreparation an amountof the stabilizing amine ranging up to 0.5 per cent excess of theory. Onthe other hand, if it is desired to produce a soluble diazoaminocompound, a greater excess of the stabilizing amine is required, rangingup to 2.62 mols to 1 mol of the diazonium compound. If the amounts ofthe stabilizing amine exceed the proportions given, the sensitivity ofthe recording solution is thereby substantially depressed. It istherefore advisable to bear these ratios in mind in compounding thestabilized diazonium compound.

One of the particular advantages in the utilization of the diazoam-inocompounds is that they may be: utilized either in the form of water-insoluble compounds or in the form of water-soluble compounds.Previously, stress has been placed upon the fact that compounds such asbenzidine, dianisidine, and the like are primary aromatic amines whichupon diazotization and coupling yield dyest'ufis simulating shades ofblack. By employing the diazoamin'o compounds rather than by proceedingaccording to the el'ec-- trolytic' diazotization and coupling method, itis possible to use such amines in the preparation of the records. Theutilization of the d-iazoami-no compounds, therefore, permits theelectrolytic recording method to be expanded to include the utilizationof those normally water-insoluble primary aromatic amines which havebeen found to yield the darkest shades of dyestuffs.

In the dyestufi art, it is normally not desired to utilize water-solubled-iazoamino compounds which have the solubilizing group in the originaldiazonium nucleus for the reason that these cornpounds upon coupling donot give dyestuffs of the fastness required in the textile industry;However, for the preparation of records by the electrolytic method, itis desirable to use such water-soluble compounds for the reasonthat-during the electrolytic action dyestuffs are produced having afastness' sufficient for the facsimile recording art.

Water solubility of the diazoamino compounds may be efiected either byincluding water-solubilizing groups in the primary aromatic amine whichis to be diazotized, in the stabilizing amine, or in both.. Forinstance, diazotized naphthionic acid coupled with sarosine will give awater-soluble product in which solubilizing groups are present in boththe diazoniu'm compound and in kfalinit'y can be efiected by theutilization of in-' organic hydroxides, such as sodium hydroxide,potassium hydroxide, or the like.

, Other ingredients may also be employed to fac'ilitate the operation.Thus penetration of the receiver by the recording composition isfacilita'ted by the use of a wetting agent such as alkyl naphthalenesul'ion'ic acids, for example but'yl naphthalene sulfonate and the like,the condensation product of asulfonated benzene with chlorinatedkerosene, sarcosines and taurines, the N- atom of which is acylated witha high molecular weight fatty acid for example oleic, palmiti c and thelike.

Improved half tones are ensured by using a buffering agent in therecording composition The buiiering agent may be b'orax, sodium acetate,sodium carbonateor the like.

Where a question of stability is involved "this can often be resolved byresorting to the use of reducing agents such as hydrazine, hydroXylamine and the like. While the reagents enumerated above are notessential, they will in some instances lead to an improved process andthe formation of improved images, and their use in general isrecommended. 7

The receiver may be prepared for the electrolytic treatment in variousways. It may, for instance, be impregnated with a solution of theaforementioned essential ingredients and subjected to the action of anelectrolytic current. On the other hand, the receiver may impregnatedwith an organic solvent solution of a watch-in soluble diazoaminocompound, such as analcoholsolution, and the receiver subjected to anelectric current in an electrolyte solution containing the coupler.Furthermore, a paste may be made of the components, the paste applied tothe receiver, and the receiver subjected to electrolysis in anelectrolyte solution. The invention contemplates the utilization of anymethod for bringing a receiver under the influence of an electrolyticcurrent in the presence of a stabilized diazonium compound, anelectrolyte and a coupling compound so as to effect a springing of thediazonium compound from the 'di'azoamino compound and a coupling of thesame with the coupling compound to produce dye images in consonance withthe impulses imposed upon the electrolytic cell. However, it has beenestablished that the most practical method of carrying out the inventionis to employ anelectrolyte solution containing a soluble diazoaminocompound and a soluble coupler. Such as electrolytic solu- An apparatusby which the invention-may be effected is diagrammatically disclosed inthe accompanying drawing.

ON rm: DRAWING Referring to the drawing, it will be seen that theapparatus comprises a drum A mounted on a drive shaft 0. The drum isprovided with a helix B which is made of a conducting material and isconnected in any appropriate manner, such as through the drive shaft Cto ground D.

The signals representative of the image to be recorded are applied onthe grid of an output amplifier tube E, the anode Y of which isconnected to a positive source of voltage F and the cathode G of whichis connected to the printer bar H. By this arrangement, output signalsfrom the tube are taken across the cathode output resistor J, one end ofwhich is connected to the cathode G and the other to ground D. Thecarrier K which is a traveling web or band of paper or fabric, movesintermediate the printer bar H and the drum A. The carrier K isimpregnated with an electrolytic solution comprising a stabilizeddiazoamino compound, an electrolyte and a coupler.

When current flows through the printer bar to the ground through thepaper K and the helix B, the diazoamino compound is decomposed with theformation of a diazonium compound, and coupling ensues between thecoupling component and the diazonium compound, with the formation of adye. The dye will appear in a concentration dependent upon the impulsesto which the printer bar is responsive.

The helix is the cathode or negative element of the cell and is usuallyformed of berylliumcopper alloy, stainless steel or platinum. Theprinter bar, on the other hand, constitutes the anode element and isusually formed of platinum, platinum-iridium or stellite. The quantityof dye which is produced by the current passing between these elementsis in proportion to the current flow and the time it is flowing and isdetermined by coulombs per square inch. The current flow is generally soset that a maximum depth of recording is represented by full currentfrom the tube. Lower values of current give half tones. While the colorformed is proportional to the current flowing, this proportionality isnot necessarily linear.

I have previously referred to the fact that it was known in the dyestuffart to decompose diazoamino compounds to regenerate the diazo niumcompound for coupling by resorting to the utilization of steam, acidvapors, strong acids and the like. There is, however, a very markeddistinction between the procedure adopted for use in the dyestufi' artand the course of the reaction in my present electrolytic recordingmethod. In the dyestufi art the whole fabric is permeated with thedecomposing agent and should this be acid the entire fabric becomesacidic and remains so until the acidity is neutralized by theutilization of an alkali. In other words, the acidity is permanentrather than fugitive. The degree of acidity is uniform throughout.Consequently, if the fabric is uniformly impregnated with the diazoniumcompound, upon treatment of the fabric with a coupler and thedecomposing agent the fabric will be uniformly dyed throughout.

It the electrolytic method, on the other hand, the color is developedonly on one surface of the receiver. the electrolyzing current flowsthrough the fabric between the electrodes, only a very small Thus if thereceiver is a fabric when,

part of the receiver, 1. e., that which is in direct contact with thesurface of the printer bar (anode) and which is backed by the helix(cathode) becomes acidic. The reverse side of the fabric becomes morealkaline. This condition, however, is only transitory for as soon as thecurrent flow ceases the acidity is lost completely and alkalinity isautomatically restored. The time of the current flow for any oneparticular spot is exceedingly small, being less than $1 of a second fornormal recording speeds. The degree of acidity is variable beingdependent on the current and the time of flow, and this mechanism thuspermits a gradation in the amount of color formed, whereby theproduction of half tones is made possible. Such procedure is impossiblein the dyestuff art since a gradation in the amount of color can only beeffected in that method by limiting the amount of the diazoaminocompound or coupler in the fabric and cannot be effected by control ofacid development of the color.

There are other factors existing which also serve to distinguish theelectrolytic method, on the one hand, from the prior art dyestuffmethod, on the other hand. The degree and permanence of acidity in theelectrolytic method, as previously pointed out, is not comparable to thedegree and permanence of acidity in the prior art method. Whether it isthe acidity which prevails at the anode in the electrolytic method bywhich decomposition of the diazoamino compound results is not known andhas not been ascertained. It is known, however, that during electrolysisa strong oxidizing action is present. This oxidizing action probablyplays some part in the breaking of the diazoamino compound since the artrecognizes the fact that many organic linkages are broken by the actionof strong oxidizing agents.

Furthermore, during electrolysis nascent chlorine and oxygen are presentso that in addition to the formation of the dye by coupling, sidereactions undoubtedly ensue. These other reactions influence the courseof the reaction, particularly with regard to the shade of the colorformed. It is thus evident that the procedure herein contemplated cannotbe considered even analogous to the prior art procedure of producing azodyestu'lf from coupling compounds and stable diazoamino compounds.

Considerable attention has been paid above to the various types ofcoloring which produce background impermanence in electrolyticrecording. It was stated that the coloring apparently attributable tooxidation and polymerization of the coupling compound is facilitatedwhen there is present in the electrolyte a component having a primaryaromatic amino group. Very surprisingly, however, the diazoaminocompounds which are per se stable to light, exert a stabilizing actionto light upon the coupler precluding to a farreaching extent theaforesaid discoloration attributable to oxidation and polymerization.This,

of course, means that after the electrolytic treatment the recordsobtained are much more permanent in their background on exposure tolight than the records obtained by other electrolytic methods. Anindication of the degree to which the diazoamino compounds affectbackground stability may be seen from the fact that records made withthe best solutions for the electrolytic diazotization type recordingshowed more discoloration when exposed to light for one day'than recordsmade according to the present method andexposed to light for one month.The diazoai-hlino ctlirnpounds,- therefore,- have some verypeculiaraction onthe coupling agents which leads to high light stabilityof the records, a fact ii hich could never have been deduced from thenonanalagous employment of the diazoamino com-pounds in the dyestufi artin general.

The peculiar action of the diazoarnino compounds in assuring backgroundpermanence is also brought home by this further finding. In

the electrolytic diaz'otization method, attempts light and this isparticularly true when the ratio between the diazoamino compound and thecoupler is maintained substantially constant. The importance of thisfactor cannot be overemphasized; since it solves one of the veryannoying problems dealing with the shade of color which is alwaysincidental to the utilization of the other terms of electrolyticrecording.

The iollowing examples will serve to illustrate my invention, althoughit is to be understood that the invention is not restricted thereto.

Examp I 24.4- grams of dianisidine are slurried in 40cc. of 38%hydroclhloric acid and after being thoroughly wetted out, aDprO motel?500 grams of water and 500 grams of ice are'added thereto.

.3.8 grams o s dium n r te are ii ss vccl i a mallam unt f wat r a d eso ut on s ru in o th slurry at a temp r ur of l to 15 C- An excess ofnitrous acid is maintained for half ar hour and then is removed by theaddition of a small amount of sulfamic acid. This procedure 4 can befollowed by spot tests on starch=i0dide paper.

grams of activated charcoal are then added the solution stirred forminutes. The solution is then filtered.

The tetra ized di ni id n hus obt i is hen added slowly to a o -fiqnl 2.ams o diethanolamine and, 36.8 grams of soda ash in 600 parts of Waterwhile rapidly agitatin ,A reaction temp ratur of, .10 to 15 .C- s, mntain d. T

. s olution of the diazoarnino compound is made in ethyl alcohol and thereceiver treated therewith either rimmer n o by sp a i ie- A rec d nolution {o us i h th t eated pap s the madeupby d sso in =01.. ram mo ei; hromotrop c acid and 3.0 grams of salt. a liter of water. Sufli-centsodium ht he solution to i e it ed solution is then used r01;'wottiilglih use.

whereupon the paper is passed through an apparatus of the type abovedescribed for the'formation of dyestuff images thereon.

The dyestufi images obtained are dark blue brilliant images on a yellowbackground. The background is highly resistant to color changes.

Similar results were obtained when utilizing in lieu of the chromotropicacid coupler, the following couplers:

p-Suliophenylmethyl pyrazolone H @019 E eny 1 acid .Chloro 1-]: acid l=naphthol-4.8disulionic acid Ace H a i Beta naphthol N h olR Ethylatfidbeta naphthol and a mixture of chromotropic acid and diacetoacetylethylene amin Example II 2.4' grams of Naphthol AS are mixed with 1.28grams of sodium hydroxide (in the form of a concentrated solution) andcc. of boiling water are poured over the mixture to give a colorsuspension. After cooling to room temperature,

2 grams of a 40% solution of formaldehyde are added and the mixturediluted to a volume of cc.

Recording paper is treated by immersion in the above composition. Thepaper is then coated W th a p is lfi made by mixi the dry dia a compoundof Example I with sufiicient diethanolamine to give the desiredconsistency.

This paper is then passed through a slightly alkaline solution of saltand water and. subjected to the action of an electrolytic current in theapparatus described above. There are formed on the paper, dyestufiimages which are dark blue to purple in color on a. yellow backround.The records show a high background stability to light.

It will be appreciated that in this example both the diazoamino compoundand the coupler are water-insoluble, but despite this fact, verysatisfactory records are nevertheless obtained.

Example III .5 gram mole of sodium naphthionate is dissolved inapproximately 750 cc. of water to which sufiicient sodium hydroxide isadded to make the solution alkaline to brilliant yellow test paper.

.5. gram mole of sodium nitrite is then added and the solution is rununder rapid agitation at a temperature of 5 to 10 G. into a solution of141) .cc. of 38% hydrochloric acid and 750 cc. of water and ice.Diazotization is complete almost as soon as the solution is added andthe diazonium compound, which is quite insoluble, precipitates out as athick, creamy slurry. Stirring is continued for one hour to obtain theproduct in a form in which it is more easily ,filtered, Filter cakeobtained upon filtration is reslur-ried in approximately 500 cc. ofwater until a smooth paste is obtained. This paste is added slowly at 10to 15 C. over a. two-hour period with rapid; agitation to a solution of.125 cc. of diethanolamine in 250 cc. of water while mainmining, a emeratute f. 0 to 15 c. in an ice bath to nimize decomp sition- Thereaction is complete when all the diazon-ium compound has been added.The resulting solution is. amber in colorand may stain diluted to 1liter.

'and salt is used to impregnate papera 13 paper with a reddish tint. Itmust be alkaline when tested with brilliant yellow test solution.

2 grams of sodium hydrosulfite are added and the solution stirred forone hour at room temperature to clear away the red-staining impurities.2 grams of activated charcoal are incorporated and the temperatureraised to 50 to 55 C. for hour for the purpose of further clarifying thesolution and to remove basic impurities. The solution is then filteredand the volume is adjusted to 1000 cc.

.A recording solution is then prepared by dissolving .03 mole per literof the monosodium salt of chromotropic acid in 500 to 700 cc. of water.8 grams of sodium carbonate are then added to render the solutionalkaline to test with brilliant yellow test solution. .06 mole of theabovedescribed diazoamino compound, 30 grams of salt, and .5 gram of asulfonated benzene which has been alkylated with a chlor paraflin andwhich is sold under the trade name Nacconol NR are then added and whensolution is complete, the same is filtered and diluted to 1000 cc. Thefinal solution is adjusted to a pH of 10 to 10.2 by the addition ofapproximately cc. of 2 N. sodium hydroxide solution. Dark blue to purplerecords on a white background are obtained when paper impregnated withthis solution is subjected to the action of an electrolytic current.

Example IV Example In and grams of salt are then added and the solutiondiluted to 1 liter.

Papertreatedwith this solution and subjected to an electrolytic currentin the apparatus previously described will give records of the typereferred to in Example III.

Example V .03ngram mole of ethylated beta ethoxy-LG- Cleves acid isdissolved in about 300 cc. of water with the addition of suflicientconcentrated sodium hydroxide solution to give a pH of approximately 10.

.03 gram mole of the diazoamino compound of Example III and 30 grams ofsalt are added and the solution Sufficient sodium hydroxide is added togive a pH of 10.2. The results-of using a paper impregnated with thissolution approximate those of Example 111.

Example VI 4'-diethanolamino-4-amino-azobenzene is converted into astable diazoamino compound by means of diethanolamine while operating inthe manner outlined in the preceding example. A solution of thiscompound with chromotropic acid Dark recordings with a stable backgroundare thus obtained.

Example VII The procedurein this example is the same as in Example Iexcepting that the diazonium compound which is stabilized istetrazotize'd benzidine.

ill)

Example VIII The procedure in this example is the same as in Example Iexcepting that the diazonium com-- pound which is stabilized istetrazotized dianisidine.

Example IX The procedure in this example is the same as in Example IIIexcepting that there is used in lieu of the naphthionic acid diazotizedalpha naphthylamine-4.8-disulfonic acid.

Example X One mol of dianisidine is tetrazotized and stabilized byreaction with 2.62 mols oi sarcosine while following the procedureoutlined in Exampie I. The resulting diazoamino compound is utilized inconnection with the coupler composition of Example II to produceelectrolytic azo dyestuif images.

Example XI Anthranilic acid is diazotized and stabilized with a 5%excess of diethanolamine. The resulting compound is used in lieu of thediazoamino compound of Example III.

Example XII 1 mol of naphthionic acid is diazotized and stabilized with2.62 mols of 2.5-dihydroxy-dicyclohexylamino-3-carboxylic acid whilefollowing the procedure disclosed in Example III. The resultingdiazoamino compound is then incorporated in the solution of Example IIIin lieu of the diazoamino compound thereof.

Example XIII 1 mol of diazotized naphthionic acid is stabilized by meansof 2.62 mols of p-hydroxycyclohexenyl glycine while utilizing theprocedure described in Example I. The resulting diazoamino compound isused to substitute the diazoamino compound of Example III. The procedureis otherwise the same as in Example III.

Example XIV 1 mol of diazotized naphthionic acid is stabilized by meansof 2.62 mols of gamma-hydroxy piper-idine while following the procedureof Example III. The resulting diazoamino compound is used to replace thediazoamino compound of Example III. Otherwise the procedure is as inExample III.

Example XV Example XVI The procedure is the same as in Example IIIexcept that the diazotized naphthionic acid is stabilized withcyclohexylamine.

Ea'ample XVII The procedure is the same as in Example III except thatthe diazotized naphthionic acid is stabilized with 4-sulfo-aminobenzoicacid.

It is to be understood that various modifications of my invention willbe apparent to persons skilled in the art and I therefore do not 15intend to be limited in the patent granted except as required by theappended claims.

I claim:

1, The process of producing colored images on a relatively stablebackground on only one side of a travelling fibrous carrier by theelectrolytic facsimile recording method which comprises impregnating thecarrier with an aqueous a1- kaline azo dye forming compositioncomprising as its essential ingredients a diazoamino compound stable tolight and air oxidation in an alkaline medium and splitting under theinfluence of the electrolytic recording current to yield diazonium ions,said compound being selected from the class consisting of those of thefollowing formulae R1 A N=NN\ R2 and wherein R1 andv R3 are selectedfrom the class consisting of hydrogen, aliphatic, araliphatic,cycloaliphatic and aromatic radicals, R2 and R4 are selected from theclass consisting of aliphatic, aralipha-tic, cycloaliphatic and aromaticradicals, A and A are aromatic radicals, Z represents the atomsnecessary to complete a nitrogenous heterocyclic ring system, and a: isselected from the class consisting of 1 and 2, a water soluble inorganicsalt as the electrolyte in an amount sufiicient to facilitate thepassage of the electrolytic recording current, and a sufficient quantityof a coupling component to react with said diazonium ions when formed toproduce an azo dye, and subjecting the so treated carrier to the actionof an electrolytic recording current.

2-. The process as defined in claim 1 wherein the diazoamino compound isthat from diazotized naphthionic acid and cyclohexylamine and thecoupling component is chromotropic acid.

3. The processas defined in claim 1 wherein the diazoarnino compound isthat from diazotized naphthionic acid and 4-su1fo-2 aminobenzoic acid,and wherein the coupling component is chromotropic acid.

4. The process as defined in claim 1 wherein the diazoamino compound isthat from diazotized.

116 naphthionic acid and mornholine and wherein the. coupling componentis chromotropic acid...

5. A process as defined in claim 1 wherein the-diazoamino compound andthe coupling component are Water soluble.

6. The process as defined in claim 1 wherein the diazoamino compound andthe coupling. component are water insoluble. 7. The process as definedin claim 1 wherein the diazoamino compound is prepared from 1 mol of adiazonium compound and from 1.05 to 2,62 mols of an organic amine.

8. The process as defined in claim 1 wherein the composition contains abufiering agent.

9. The processas defined in claim 1 wherein the composition containssodium carbonate.

10; The process as defined in claim 1 wherein the. diazoamino compoundis prepared by interaction of one mole. of a diazonium compound with anexcess of an organic amine overthat necessaryto react with saiddiazonium compound.

11. The process of producing colored images with a relativelystablebackground on only one side of a traveling fibrous carrier :by theelectrolytic facsimile recording method, which com.- prises impregnatingthe carrier with an aqueous alkaline azo dye forming compositioncomprising as its essential components a diazoamino. compound stable tolight and air. oxidation in an alkaline medium and splitting under theinfluence of the electrolytic recording current to yield diazonium ions,said compound having the following formula wherein A and R1 are aromaticradicals and. x is a positive Whole number not greater. than 2,. a watersoluble inorganic salt as the electrolyte in an amount sufiicient tofacilitate the passage of an electrolytic recording current, and asuificient quantity of a'coupling component to react with said diazoniumions when formed to produce an wherein Z represents the atoms necessaryto complete a heterocyclic nitrogenous ring system, A is an aromaticradical, and a: is a positive whole number notgreater than 2, a watersoluble inorganic salt as the electrolyte in an amount sufiicient tofacilitate the passage of an electrolytic recording current, and asufiicient quantity of. a coupling component to react with saiddiazonium ions when formed to produce. an azo dye, and subjecting the sotreated carrier to the action of an electrolytic recording current.

HAROLD G. 'GREIG.

(References on following page) 17 18 REFERENCES CITED Number Name DateThe following references are of record in the 2232406 schmelzer 1941 meof this patent: 2,306,471 Solomon Dec. 29, 1942 2,354,088 Reichel July8, 1944 UNITED STATES PATENTS 5 2,419,296 Solomon Apr. 22, 1947 N m rNam D t OTHER. REFERENCES 1 22 235 et a1 g? The Aromatic Diazo-Compoundsand Their 1982631 Markus}; 1934 Technical Applications by K. H.Saunders, Du 26 81 C0. Pp. 2,058,419 Dahlen et a1. Oct. 25, 19362,232,405 Schmelzer Feb. 18, 1941

